Natural photosynthesis has mastered photon capture under very weak illumination, for example at 100 m below sea level. The natural chromophores used for this cannot be reproduced in the laboratory, and are very fragile and difficult to handle.
Light has been collected efficiently in nature itself for at least 2.5 billion years. To date, similar achievements have been made only by the building of large light-collecting antennas or by self-assembly of fully synthetic molecules, for example, as described in DE 101 46 970 A1, which is incorporated by reference herein.
Phthalocyanines are stable dyes which have good pigment properties, for example, high absorption coefficients in the visible range. Attempts to date to incorporate phthalocyanines into dye-sensitized solar cells have yielded only very low efficiency, for example, low power conversion of light to electrical current. A problem may lie in the tendency of the dyes to aggregate, which leads to quenching of the fluorescence. Therefore, phthalocyanines typically result only in a radiationless deactivation process.
Conventional silicon-based solar cells, even though they exhibit good efficiency owing to the complex purification processes, are too expensive to build large-area systems. Dye-sensitized solar cells, in contrast, exhibit a significantly lower efficiency, but are producible with low production costs.